This invention relates to endoscopic surgical devices. More particularly, the invention relates to an endoscopic surgical tool having end effectors made out of a combination of plastic or ceramic and metal and useful for selective endoscopic cautery.
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical tools may be inserted through the tubes. A camera, magnifying lens, or other optical instrument is often inserted through one trocar tube, while a cutter, dissector, or other surgical instrument is inserted through the same or another trocar tube for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon via the optical instrument in place in the trocar tube.
Various types of endoscopic surgical instruments are known in the art. These instruments generally comprise a slender tube containing a push rod which is axially movable within the tube by means of a handle or trigger-like actuating means. An end effector is provided at the distal end of the tube and is coupled to the push rod by means of a clevis so that axial movement of the push rod is translated to rotational or pivotal movement of the end effector. End effectors may take the form of scissors, grippers, cutting jaws, forceps, and the like. Because of their very small size and the requirements of strength and/or sharpness, end effectors are difficult to manufacture and are typically formed of forged stainless steel. As such, they form an expensive portion of the endoscopic instrument.
Modern endoscopic procedures often involve the use of electrocautery. Indeed, several types of electrocautery devices for use in endoscopic surgery are described in the prior art. U.S. Pat. No. 4,418,692 to Guay, for example, discloses a device for use in laparoscopic tubal cauterization for blocking the Fallopian tubes of a patient. The device comprises a substantially tubular body member having a spring-biased piston slidably mounted therein. A pair of electrodes (either monopolar or bipolar) are disposed to grasp living tissue when the piston is in a first position biased by the spring and to release the tissue when a button is pressed which moves the piston into a second position. The device includes a circuit breaker which interrupts current flowing to the electrodes when the piston is in the second position. When the electrodes grasp the tissue, however, current is supplied to the entire surface of the electrode, that is, both the grasping surface and the outer non-grasping surface.
Another electrosurgical instrument for use in combination with an endoscope is disclosed in U.S. Pat. No. 5,007,908 to Rydell for "Electrosurgical Instrument Having Needle Cutting Electrode and Spot-Coag Electrode". Rydell's device includes an elongated flexible tubular member with a plurality of lumens. The distal end of the tubular member is provided with a bullet shaped ceramic tip covered with a conductive layer and having an opening coupled to a first one of the lumens. The conductive layer is coupled to a conductor which extends through a second one of the lumens to an electrical source. A second conductor, also coupled to the electrical source is slidable through the first lumen by a plunger. The two electrodes form a bipolar pair. In a second embodiment, the conductive layer on the ceramic tip is split by an insulating gap and both halves of the tip form a bipolar pair of electrodes. As with the Guay device, above, substantially the entire distal surface of Rydell's device serves as an electrode when energized.
Other electrocautery probes for use with an endoscope are disclosed in U.S. Pat. No. 3,920,021 to Hiltebrandt. Hiltebrandt discloses several types of probes similar to Rydell's in that they have a substantially bullet shaped tip with hemispheric or annular conductors forming electrode pairs. Hiltebrandt also shows electrodes similar to Guay's; a pair of springy arms slidable through a tube member to grasp and release tissue. Of course, the gripping force obtainable by either Guay's or Hiltebrandt probes is severely limited because the electrodes must be "springy".
It is known in electrosurgery to insulate a portion of the surface area of an electrode so that only a precise or at least well defined portion of an electrode's surface is conductive. This is desirable in order to protect both the surgeon and the tissue adjacent to the site of electrosurgery from accidental cautery by an electrode having a broad fully conductive surface. U.S. Pat. No. 3,100,489 to Bagley, for example, shows cautery forceps where the entire surface of the forceps with the exception of the forceps tips is provided with an overall pliable insulating coating of rubber or synthetic rubber-like material. U.S. Pat. No. 5,049,148 to Mehl discloses a "Radio Frequency Hair Removal Tweezer" which includes insulated tweezer arms with conducting pads at the tips of the arms so that RF energy can be applied to individual hairs without burning surrounding skin through arcing. Nevertheless, it is heretofore unknown to selectively insulate portions of an endoscopic end effector to provide a well defined and discrete electrosurgical surface. It is also heretofore unknown to make endoscopic end effectors primarily from plastic, as plastic is typically considered too weak to properly serve desired functions.